A multiple-part drive shaft for the chain drive of a chain scraping conveyor consisting of a main shaft with unilateral or bilateral internal gearing for accommodating externally geared stub shafts for the gearing connection and a chain sprocket fastened on the main shaft for interaction with the conveyor chain band.
Chain drives for chain scraping conveyors in heavy-duty coal mining sprags in accordance with the state of the art consist of a drive framework in the side walls of which the drive shaft is mounted. The drive shaft in this connection consists of a main shaft to which the normally externally geared chain drum--henceforth designated as the chain sprocket--is normally constructed in two parts with half shells. The attachment takes place there with a friction-locking clamp fit, in connection with which bilateral rows of screws with highly prestressed screws generate the necessary clamping force and consequently the clamp fit. Through the high compression between the main shaft and the attached chain sprocket, considerable torque is transmitted, causing friction locking between the main shaft and the chain sprocket. This, however, requires a corresponding number of highly prestressed screws. For this reason, making the connection more transmission-fast through additional form-locking measures, for example with adjusting springs or sunk keys, was also undertaken early.
The chain sprocket, which is fastened to the main shaft, has tooth-like star-shaped spines which offer geometrically adapted engagement possibilities to the chain links of the chain band and its position. Through the form-locking interaction of the radially arranged teeth of the chain sprocket with the chain band, the tangential force of the main shaft is transmitted through the chain sprocket to the chain band on the engaged teeth of the chain sprocket.
For this, it is necessary to have an exact agreement between the pitch of the teeth mounted on the chain sprocket and the spacing of the chain link strands forming the chain band.
The chain drive system is a component system of the chain scraping conveyer whose object is to transmit the traction into the chain band that is necessary for overcoming resistance to motion. The chief function of the chain drive is thus the transmission of the requisite traction and the transmission of the momentum of the drive machine to the working machine and the rerouting of the direction of the motion of the chain band transmission element. The chain drive component proper consists of two subassemblies:
The drive shaft, which transforms the rotatory effort into translatory effort and thereby alters the direction of force and motion, and PA1 The chain band, which serves to transmit force as well as to transmit spatial and temporal change of position to the fixtures.
These two subassemblies possess measurements synchronized with each other which are set down in DIN and factory standards.
With the main shafts of older design, it is a question of one-piece shafts with unilaterally or bilaterally overhanging externally geared shaft butts on which the gear outlet of the subsequently interposed gearing constructed with internal gearing can be pushed back. The more advanced solution variant provides internal gearing on the end(s) of the main shaft with which the form-locking connection to the gearing, and therewith to the driving machine, is produced through inserting externally geared stub shafts.
With the chain bands used today in heavy-duty coal mining sprags of type DMKB or MKB with standard sizes of 30.times.108, 34.times.126 or even 38.times.137 on the face conveyors (DMKB: Double center chain bands; MKB: Center chain band), initial stress forces of, in part, considerably more than 100 kN occur for buttressing lengths of ca. 200 m.
These initial stress forces are exceeded several fold by the operating forces, depending on the drive of the conveyor in the state of rest, and occasionally attain values of over 500 kN.
These values make it clear what tangential forces must be effectively transformed in the flux of forces between the main shaft, chain sprocket and chain band in order to apply the necessary chain forces in the chain band.
The chain sprocket, constructed in accordance with the state of the art in two parts with half shells, attempts to guarantee this flux of forces in a form- and friction-locking manner. This is brought about by the main shaft and one half shell of the chain sprocket being provided with a keyway into which a coiled spring is forced when the screws are tightened. In addition, the half shells of the chain sprocket are clamped to the main shaft when the screws are tightened. In order to realize the flux of forces securely, the required number of screws and their nominal diameter has, however, already reached an extent such that roundings-off at the tooth roots are unavoidable for reasons of space.
This has a correspondingly weakening effect on the strength of the tooth root, and on the creep strength and consequently the service life of the chain sprocket, and is contrary to the goal of a configuration which meets the requirements.
It is therefore the object of the invention to configure the main shaft/chain sprocket in such a way that the flux of forces and the torque to be transmitted is mastered without the disadvantageous consequences of reducing service life and therewith also of the operational charging time as a consequence of tooth-root weakening that has arisen through the concrete design of the main shaft/chain sprocket connection.